Carbohydrates are important nutrients used as our energy source. When taken, the carbohydrates are digested by enzymes in the gastrointestinal tract and absorbed in the small intestine. As a result, blood glucose levels increase. In the case of healthy individuals, when blood glucose levels increase, insulin is secreted from the pancreas to lower blood glucose levels. On the other hand, in the case of diabetic patients, the blood glucose levels continue to stay high because a required amount of insulin is not produced or secreted, or because, even when secreted, insulin has decreased effects. Diabetes mellitus is divided into type I and type II. The former is characterized by insulin not being produced due to genetic causes whereas the latter is characterized by reduced abilities of insulin secretion or decreased effects of insulin due to lifestyle such as obesity, lack of exercise or the like. Among the diabetic patients, 90% or more are those with type II diabetes mellitus. Recently, these patients with type II diabetes mellitus have been rapidly increasing, which becomes serious social concerns. Prevention of diabetes mellitus thus attracts much attention. It is considered that type II diabetes mellitus can be treated or the onset thereof can be prevented mainly by changing one's dietary life for the better.
At present, carbohydrates used commonly in food products such as starch, starch decomposition products or the like are quickly digested and absorbed and, when taken, produce a rapid rise in blood glucose levels. Such materials are unsuitable for diabetic patients and carbohydrates that are more slowly digested and absorbed and produce a gradual rise in blood glucose levels are wanted. (It is prerequisite that their energy coefficient is 4 kcal/kg which is same as that of carbohydrates.) In addition, when used as carbohydrates in nutritional supplement products or the like, glucose or the like has a high osmotic pressure, which induces osmotic diarrhea. Thus, ones with as low an osmotic pressure as possible such as dextrins obtained by hydrolyzing starch with acids or enzymes is wanted. Accordingly, development of carbohydrates that are insusceptible to digestion and have a lower osmotic pressure is extremely helpful for diabetic patients. Further, carbohydrates that are insusceptible to digestion and have a lower osmotic pressure can also be used as a carbohydrate source for diet food products, energy supplement drinks, nutritional supplement food products and the like. Developing those is extremely significant.
As carbohydrates for nutritional supplement products that meet those needs, isomaltulose has been known. Isomaltulose is a disaccharide in which one molecule of glucose and one molecule of fructose are linked via an α-1,6 bond and a carbohydrate whose rate of digestion and absorption in the small intestine is slower, and is at present utilized as carbohydrates used in some nutritional supplement products. Yet, an aqueous solution of 10% by mass isomaltulose shows an osmotic pressure of as high as about 340 mOSMOL/kg, which in some cases limits its use.
Moreover, a highly branched dextrin characterized by having a structure in which glucose or isomalto oligosaccharide is bound to a non-reducing terminus of a dextrin via an α-1,6 bond and having a DE value of 10 to 52 (hereinafter also referred to simply as highly branched dextrin) has been disclosed (Patent Document 1). This highly branched dextrin exhibits a slower rate of digestion and absorption in the small intestine, and a 10% by mass aqueous solution thereof shows an osmotic pressure of 70 to 300 mOSMOL/kg, which is low. It may thus be used as carbohydrates in nutritional supplement products. Yet, its GI value which was considered as an index for a rise in blood glucose was not necessarily satisfactory.
Furthermore, it has been reported that, when taken concurrently with other carbohydrates such as sucrose, glucose, high-fructose corn syrup, dextrins and/or branched dextrins, isomaltulose exerts an effect of making digestion and absorption of those carbohydrates more gradually and suppressing a rise in blood glucose (Patent Document 2). However, Patent Document 2 shows no examples for actual evaluation of such an effect on blood glucose levels in cases where isomaltulose is used in combination with dextrins or branched dextrins, and it merely discloses examples with sucrose or glucose being used.